Manufacture of pure aluminium oxide



no Drawing. Application filed November 13,1928;

FIB areseparatedand removed as ferr c-silicon.

l atented Apr; 12,1932

YEIIGHIZTATSUI YIlI, vor;1Antwan-Kn, TOKYO, AND mexrsnmmo IKEBE mun xozrmo:

i O'KAZAKL1OF KTOYOTAMA-GUN, EOKYQJAPAN, ASSIEGNORS"TO MITSUI-MINIENG 605 .MAnuFAcrunE' jor roan T-ALUMINIUM mm: 1

5 Our inventionrelates to the manufacture of aluminium'oxideofi a high degree ofizpurity,

and has for its object to reduce the cost of manufacture of such compound :in-- a highly lb ti vely-large quantity ismixed with=aluminous materials such as-clay, agalmatolite, diaspore, on bauxite, I and the mixture is heated and fused in' a-nelectric-furnace, whereby the silicic acid and the iron-of-theseraw materials 'To the reacting :mixture are also i added lime and large quantitiesofcarbon',theimpure alumi iumoxide so obtained containingalu- Irrinium ca-rbide and "calcium 1 carbide as purities. The crude product is then suitably treated to separate and remove ithevcarbon and calcium contained in the aluminium carbide, calcium-carbide and lime.

'lhe process, aims at producing a impure aluminium :oxide :first at a smallexpense with a minimum ofele'ctric power, andthen puritying gsuch oxide :at La small cost, :whereby aluminium oxide -is produced in an .easyand economical manner.

' 1 Forthe' purpose of making aluminium oxide in an electric'ffurnacei fromaaluminous materials, such as clay, agalmatolite,5diaspore and 1bauxite,-a great amount of electric power is ordinarilyrequired. iMoreover J the product is not-made easily and the: cost or pulverization is: very great, It is very; difiicult to obtain aluminium oxide :of more than 96 purity by, any known: purely I electrical processes, For these reasons such processes have mot beenadoptedzhithertofor the manufacture ofaluminiumioxide. e V o According to the present invention, a practical and easily conducted process for obtainingipurealuminium oxide at a reduced cost is provided as, follows: Large quantities of iron, iron oxide or mag} 'netic pyrite'are added to the above mentioned 'aluminous materials, an'dat' thesame time large" quantities of carbonaceous i'substances,

suchgas, coke on'anthracitecoal, and some *lime are also added to them; .i p The mixture purified state andgprovidea simple process Serial llTo. 319,182, and in Japan-November 1$,'.1.92?.

calcium lime.)

iron, respectively, by the carbonaceoussubstances, there 1 being ,"produced the easily fus ble, and separable ferro-siliconzcontaining 1 silicon r in low degree because of the The silicic acid in the clay and theiiron' oxideiarei-completely reduced to siliconxand preponderating quantity of iron addedto the original mixture. By the action o frcarbon, some, quantities of the aluminium oxide and calcium oxide are'reducedtoaluminium-carbide andlimeparbidewhich*float'*withalu minium' oxide on the surface ofthe mol-ten materialin thefurnace becauseof theizlow specific -gravity; while theferro=siliconsettles toa the bottom, so thatthe two layers may easily be separated. In this manner, :alu-

minium oxide, which' is almost entirelyfreed ofthe iifOllfiIId silicon, can be prepared; The melting point of this impure aluminium oxide is far lower than that or "aluminium oxide zas heretofore prepared in an electric fiurinacmlandxmayieasily .beattained: in :the

furnace. ,Gonsequentlythe quantity otre'lece trio powerwconsumption,.ethehmosteimportant item ofnostin thepreparationofaluminium oxide, may considerably. ..be lessened. ;The

crudealumlnium oxide which is taken out o'fpthe iurnacea and: cooled econtainsxcalcium compounds-and aluminium scar-bide, and is very rough, =when compared with 1 aluminium oxide such {21S prepared heretofore in :an elec trio-"furnace, and it may be easily pulverized in a suitable'machine. The powdered impure aluminium oxide may thenbe treated I either with hydrochloric acid or at firstzwvith steam and then with hydrochloric acid, to

separate and remove theialuminium r carbide,

lime carbide and calcium oxide toproduce pure aluminium oxlde.

' l he reactions -in' this caseare 1 as? follows The following-isanillustrationora practi= cal mode of carrying out our invention, but the same is to be understood as being given by way of example and not by way of limitation:

The percentage composition of the clay used is as follows:

Alumina 36.12 Silica 49.20 Iron oxide 3.36 Lime 0.22

To make up the reacting mixture, the following proportions (by weight) may be used:.

Clay 100 parts Iron 35 parts Coke parts Lime 1 part .After these ingredients have been mixed together, the mixture is charged into an electric furnace operating at about (1,500 kilowatts) to melt it. Impure aluminium oxide is 'thus produced and is very rough and ma easily be pulverized. Its composition is as ollows:

. Per cent Alumina 93.00 Silica 0.20 Lime 3.74 Iron; 0.01 Total carbon 2.30 The following is the composition of aluminium oxide refined by pulverizing this impure aluminlum oxide to a fine powder of less than 100 meshes per inch, and by treating it with hydrochloric acid at 10 degrees B.

Per cent Alumina 99.20 Silica 0.20 Lime 0.30 Iron 0.01 Total carbon 0.10

In short, the present invention, as above explained, facilitates the extraction of aluminium oxide, which was hitherto difficult to do in an electric furnace, and reduces the consumption of electric power. Moreover it overcomes the difiicult usually encountered in pulverizing aluminium oxide as hitherto prepared in an electric furnace. According to our'process, aluminium oxide of more than 99% purity can be produced by a subse uent simple wet treatment, and we thus 0 tain economically and easily materials for preparing white alundum or metallicaluminium. In addition, by treating the powdered impure aluminium oxide with water, aluminium carbide and calcium carbide can be decomposed to aluminium hydroxide and calcium ydroxide, so that the purity of aluminium oxide can beincreased and the oxide rendered suitable as raw material for preparing metallic aluminium.

l/Vhere in the claims we employ the term iron-containing material, the same is to be understood to include not only iron oxides or ores, but also the metal itself.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:

1. The method of producing substantially pure aluminium oxide, which comprises the stepsof heating and fusing a mixture of silicious aluminium-containing material, an iron-containing material and a carbon-containing material in an electrical furnace, thus producing an impure aluminium oxide, separating said impure aluminium oxide from the ferro-silicon resulting from the conversion of silicon, and then removing the carbon and the'calcium from the impure aluminium oxide.

2. The method of roducing substantially pure aluminium oxi e, which comprises the steps of heating and fusing a mlxture of silicious aluminium-containing materal, an iron-containing material, a carbon-containing material and lime in an electrical furnace, thus producing an impure aluminium oxide, separating said impure aluminium oxide from the ferro-silicon resulting from the conversion of silicon, and then removing the carbon and calcium from the impure aluminium oxide.

3. The method of producing substantially pure aluminium oxide, which comprises the steps of heating and fusing a mixture of silicious aluminium containing material, iron, a carbon-containing material and lime in an electrical furnace, thus producin an impure aluminium oxide, separating sai impure aluminium oxide from the ferro-silicon resulting from the conversion of silicon, and then removing the carbon and calcium from the impure aluminium oxide.

4. The method of producing substantially pure aluminium oxide, which comprises the steps of heatingand fusing a mixture of silicious aluminium-containing material, iron oxide, a carbon-containing material and lime in an electrical furnace, thus producing an impure aluminium oxide, separating said impure aluminium oxide from the ferro-silicon resulting from the conversion of silicon, and

then removing the carbon and calcium from the impure aluminium oxide.

5. The method of producing substantially pure aluminium oxide, which comprises the steps of heating and fusing a mixture of silicious aluminium containing material, iron, iron oxide, a carboncontaining material and lime in an electrical furnace, thus producing an impure aluminium oxide, separating said impure aluminium oxide from the ferro-silicon resulting from the conversion of silicon, and then removing the carbon and calcium from the impure aluminium oxide. In testimony whereof We hereunto alfix our signatures.

YEIICHI TAT SUMI. TAKISABURO IKEBE; KOJIRO OKAZAKI. 

